Whales, Dolphins Inspire Wind Turbine Tech

July 11, 2008 -- Whales' and dolphins' speed and agility are wondrous to behold -- finely tuned by evolution for efficiency and maneuverability in the water. Now researchers are working to translate these animals' natural innovations into manmade technologies on land, air and sea.

Frank Fish of West Chester University in Pennsylvania began to study the humpback whale fin while on vacation in Boston in the early 1980s, where he saw a statue of a humpback whale in a shop in Quincy Market. He assumed it was sculpted incorrectly, because the figure showed bumps along the front edge of the flipper.

"It just didn't make sense," Fish said. One of the cardinal lessons of fluid mechanics is that the leading edge of a fin or wing needs to be smooth to create the flow that provides lifting force.

Fish mentioned it to the shop owner, who pulled out a photo of a humpback whale, clearly showing the bumps in front.

"I became sort of obsessed with it," Fish said. He called around to locate a specimen to measure and model the fins, and ended up on a contact list for those interested in stranded marine mammals.

Years later, Fish got a call that a humpback whale was dead on the New Jersey shore, and he could have a fin. The fin wouldn't fit in his car and he ended up slicing it in three pieces to make it fit. "I was absolutely afraid I'd be stopped by state troopers with my car full of flesh in black plastic bags," he recalled.

The fin languished for some more years in the freezer while Fish looked for a way to make a cast of it. Eventually, he had it sliced into one-inch sections and then photographed them.

Finally, Fish had the information he needed to create and test a model of the humpback's flipper. Through modeling and wind tunnel studies done by colleagues, Fish determined that the bumps on the whales' fins do indeed serve an important purpose. Among its advantages is it overcomes what's known as "stall" -- the angle at which a wing no longer experiences lift, but only drag, so it loses its ability to act as an airfoil.

"The full fin could delay stall. It could decrease drag in certain instances, and it could improve lift," Fish said.

To feel this, imagine sticking your palm out a car window, palm down and parallel to the ground. All you feel is drag. If you start to tilt the front edge up, you feel the backward force of drag, which gets a little stronger, but you also feel the upward force of lift. If you keep increasing the angle of your hand, eventually the lift force goes away.

The whale fin can tilt to a higher angle before experiencing stall. On the whale, the delayed stall means it can make tight turns, a crucial skill for the way it hunts schooling fish like herring, swimming around them in tighter and tighter circles and then shooting up through the column of fish and swallowing them.